(function (doc, win) {
 var docEl = doc.documentElement,
      resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize',
      recalc    = function () {
          console.log('font.js')
             var clientWidth = docEl.clientWidth;
             if (clientWidth>=640) {
                clientWidth = 640;
             };
             if (!clientWidth) return;
           docEl.style.fontSize = 100 * (clientWidth / 640) + 'px';
           console.log('fontSize',100 * (clientWidth / 640) + 'px')
      };
      if (!doc.addEventListener) return;
      win.addEventListener(resizeEvt, recalc, false);
      doc.addEventListener('DOMContentLoaded', recalc, false);
})(document, window);